Nail holding device for pneumatic hammer tools



March 1954 M. H. FOX 2,671, 16

NAIL HOLDING DEVICE FOR PNEUMATIC HAMMER TOOLS Filed May 5, 1951 2 Sheets-Sheet 1 l0 8 INVENTOR. 30 MALCOLM H. FOX

A r TORNEYS M. H. FOX

March 9, 1954 NAIL HOLDING DEVICE FOR PNEUMATIC HAMMER TOOLS Filed May 5, 1951 2 Sheets-Sheet 2 INVENTOR. MALCOLM H. FOX

2 BY g MIWI Patented Mar. 9, 1954 NAIL HOLDING DEVICE FOR PNEUMATIC HAMMER TOOLS Malcolm H. Fox, Seattle, Wash.

Application May 5, 1951, Serial No. 224,737

13 Claims. 1

This invention relates to a nail-holding device for pneumatically actuated hammer tools, and more particularly to improvements in the construction of such devices for increasing the life, strengthening, simplifying and reducing the manufacturing cost thereof. This application is a continuation in part of my application Serial No. 165,089, filed May 29, 1950, now abandoned.

Another object of the invention is to provide an improved nail-driving attachment or the like for percussion tools, such as pneumatically actuated hammer tools, the improvements residing primarily in the manner of interconnecting the nail-holding sleeve element and the anvil bar or reciprocable striker element of such attachment, and in the form and arrangement of such parts.

The function of the nail-holding sleeve element employed in this general type of attachment is to receive and hold the nail, or other article to be driven, in position to be started into the work, and thereafter to retain the anvil bar in striking position relative to the nail head despite vibration and jar of the tool. Such sleeve element receives the nail within it and guides the anvil bar sliding in the sleeve bore in such manner that it will strike the head of the nail on every impact of the hammer tool plunger with such anvil bar. A spiral spring encircling the anvil bar normally urges the nail-retaining sleeve into an initially projected position in which the nai1-impacting end of the bar is received slightly within one end of the bore of the sleeve. In operation the other end of the sleeve is pressed against the work and the vibrating anvil bar is advanced progressively through the sleeve as the nail yields to the impacts and is driven farther into work. Progressively increasing overlap of the sleeve on the anvil bar is permitted by yielding of such spring.

My present invention, having various forms, several of which are disclosed herein, dispenses entirely with the use of coacting abutments on the anvil bar and guide sleeve, such as were employed in prior devices, for the purpose of limiting the maximum extension of the sleeve beyond the end of the anvil bar in the expanded position of the sleeve-engaging spring. Such abutments complicated the construction, required more component parts, and made the parts more v difficult to manufacture, assemble and take apart.

snugly but slidably in the bore of a sleeve ele- I ment. The encircling extension spring cooperating with the sleeve element slidable on such anvil bar end portion does not merely bear against the inner end of the sleeve to urge it normally into projected position but one end is actually connected to the sleeve so as to move conjointly with the sleeve in both directions lengthwise of the anvil bar. The opposite end portion of such spring is effectively anchored against appreciable movement in either direction lengthwise of the anvil bar. In this arrangement, the freely expanded length of said spring relative to the anvil bar is reached before the sleeve would be pressed past the striking end of the anvil bar by the spring. As a result the spring alone retains the sleeve on the end of the anvil bar in the desired initial or normal position. As no abutments are required to hold the sleeve on the anvil bar, these two simple components may be readily assembled by direct axial insertion of the bar into the sleeve. Preferably the spring is connected to the adjacent end of the sleeve by the movable end of the spring being threaded onto a thread formed on the exterior of the sleeves supported end, for quick detachment purposes.

In accordance with further features of the invention, several alternative arrangements are herein described for anchoring the opposite or stationary end of the spring in fixed relation to the anvil bar. The connection in each instance is of a quickly-detachable type.

A further feature of the nail-driving attachment is the provision of an anvil bar having a slender shank enabling small headed nails to be driven and countersunk while still being of rugged construction. Where the nail-driving attachment is to be used for finished nailing surfaces as distinguished from rough work, the work engaging end of the sleeve is covered with resilient rubberlike material to prevent the work surface from being marred.

These and other objects, features and advantages of the invention will become more fully evident from the following description thereof based upon the accompanying drawings.

Figure 1 is a side view partly in section and with parts broken away, showing the preferred form of my improved nail-driving attachment for percussion tools.

Figure 2 is an operating view in which the attachment, shown in longitudinal section, appears in its final operating position relative to the Work when the nail is driven home.

Figure 3 is a transverse section of the same attachment taken on line 3-3 in Figure 1.

Figure 4 is a side View corresponding to Figure 1, showing an attachment having a modified form of spring anchoring structure.

Figure 5 is a similar view of an attachment having a second modified form of spring anchoring structure.

Figure 6 is a similar view of an attachment having a third modified form of spring anchoring structure.

Figure 7 is a side View, with parts broken away, or an attachment having an alternative type of driving anvil bar or spindle and cooperating sleeve with the parts in extended position, and Figure 8 is a generally similar view of the same attachment with the parts in contracted position.

In each of the several illustrated forms of the improved nail-driving attachment, the nail-retaining sleeve clement ID receives a suflicient length or" the head end of the nail to be driven so as to support the nail for starting into the work when the tool is held horizontally, to drive the nail into a vertical surface. The sleeve also guides the anvil bar or spindle i2 to impact the nail head on each stroke of the bar. Such sleeve encircles and slidably engages the cylindrical nail-impacting end portion it of such bar as shown. The constant section portion of the sleeve bore it terminates at its inner or tool end in a flared, enlarged entrance l3. This bore entrance facilitates inserting the end of the anvil bar into the sleeve bore in assembling the parts initially. Engagement of this enlarged bore end of the sleeve with an annular shoulder is on the anvil bar limits relative contracting movement of the sleeve and the anvil bar. This occurs when the nail is driven home (Figure 2 and Figure 8). In this limiting position the driving end of the anvil bar projects slightly beyond the work-engaging end of the sleeve. The shoulder curves or fairs gradually into the adjoining portion i i of the anvil element in Figures 1 to 6, inclusive, and l 9 in Figures '7 and 8, and thereby avoids undue stress concentrations at the base or inner end of such cylindrical portion. Such shoulder conforms to the shape of the bore entrance IS, so that under mutual impact as in Figure 2 and Figure 8 there will be minimum stress concentrations.

Adjoining the shoulder 23 the anvil bar has an enlarged portion 22 which extends to a flange 24. The smaller end. or" a tapered coil spring 26 encircling the anvil bar is lodged behind this flange and extends axially in the direction of the anvil bars end opposite the sleeve ill. The body of this coil spring constitutes a female socket which can be threaded upon the working end of a percussion tool, such as a pneumatically actuated hammer tool (not shown), with the shank portion 28 of the anvil bar entering the customary open end of the tool to receive the impacts of the pneumatically actuated hammer piston reciprocated therein. The coupling spring 26 acts as the return spring for the anvil bar by snapping the latter, back toward the tool following each outward drivin stroke of the tools harnmer piston. This particular type of spring connection and the details of the tool for receiving such an attachment are conventional.

Referring to Figure 1, the coil spring 39 freely encircles the anvil bar i2 and its inner end is employed as a threaded female socket to engage threads 22 formed on a shoulder portion of the anvil bar enlargement 22. Such engagement effectively anchors such and of the spring to the bar. The outer or opposite end of this spring is similarly connected to the inner end portion of the nail-retaining sleeve I0 as shown in Figure 1. The body of the spring 30 intermediate its connecting ends is of such a length in the relaxed, expanded condition of the spring that sleeve to is projected beyond the nail driving end of the anchor bar by the desired amount, but cannot come off the bar entirely unless deliberately pulled off. This spring alone, therefore, establishes the initial longitudinal position of the sleeve on the cylindrical end portion I 4 of the anvil bar, no separate abutments or stops of any kind being necessary to limit the extension movement of the sleeve and anvil bar.

In the operation of the device the head end of a nail is inserted into the bore [6 sufliciently far that this bore will support the nail even though the bore is slightly larger than the nail head, as indicated in relation to the nail N of Figure 2. With the nail thus held the driver is advanced to engage the point of the nail with the desired location on the work. If desired, the nail shank may be steadied by the operator's hand while the nail is being started. The percussion device is then placed in operation, whereupon the nail head is struck repeated blows by the rapid vibration of the anvil bar. The driving or nail-impacting end of the anvil bar is retained in striking position relative to the nailhead by the guide sleeve l0 which encircles the nail throughout the operation. Referring to Figure 2, as the nail N is driven progressively into the work W, yielding of the spring 30 permits the cylindrical end portion M of the anvil bar to advance through the sleeve and follow the nail. The outer end of the sleeve bears steadily against the surface of the work encircling the nail to guide such bar in alignment with the nail as the latter approaches, and finally reaches, its fully driven position (Figure 2). In this latter relative position of the sleeve and anvil bar, such sleeve acts as a stop for the anvil bar, which then projects just slightly beyond the outer end of the sleeve, so that the nailhead will be set properly into the work.

In the modified nailer shown in Figures 7 and 8 the anvil bar or spindle is stepped, the major portion of its length N being relatively slender and an enlarged portion l9 being inter posed between the cylindrical end portion M and the shoulder 20. The parts [4 and I9 are interconnected by a tapered, generally conical portion I 5.

The bore I6 of the sleeve ID, in which the portion I 4 of the spindle snugly slides, is appreciably shorter than the portion [4 of the anvil bar so that when the parts are in the contracted position of Figure 8 the end of the spindle will project a substantial distance beyond the end of the sleeve, to countersink a nail being driven. In order to limit relative movement of the parts in this contracted position, not only is the entrance shaped to be engaged contiguously by the shoulder 20, but the entire bore of the sleeve I0 is stepped complementally to the spindle. Thus the sleeve includes the smaller bore portion [6 corresponding to the portion I 4 of the spindle, and the larger bore portion 20 in which the spindle portion l9 may snugly slide. These two bore portions are interconnected by the bore portion 11 which flares from the portion 16 to the portion [9 and is complemental to the tapered portion I 5 of the spindle.

The nailer shown in Figures 7 and 8 will be used primarily for driving nails in finished work.

in which it is desired to countersink casing nails, for example, such as designated N in Figure 8. In such work it is important that the surface not be marred, and consequently, instead of the work engaging end of the sleeve being tapered as in the forms of Figures 1 to 6, inclusive, such sleeve end H is flared to form a work engaging surface having an area at least several times as large as the cross sectional area of the bore IS. The corners of this flared end are rounded, and it preferably is protected from direct contact with the work by a resilient cap l3 which may beof rubber or some rubberlike material. This cap can be stretched over the end of the sleeve and held in place by tension of the rubber material, or can be bonded to the sleeve end, or may be formed in place simply by dipping the end of the tube in a suitable liquid preparation which will solidify and adhere to the end of the sleeve. In any of these cases, although the sleeve should be tilted slightly relative to the work so that its end does not seat squarely, marring of the works surface will be avoided even during the countersinking operation.

An advantage to the stepped spindle construction of the nailer shown in Figures 7 and 8 is that the spindle is enlarged at its high stress portion. In any cantilever structure the point of stress concentration is at its supported end, which in this case would be the shoulder 26. The enlarged portion I9, therefore, affords added strength and the provision of the tapered section [5 graduates the stress-carrying ability of the spindle from the part l9 to the part l4. Moreover, when a device like that shown in Figures 7 and S is used, almost invariably it will be desired to countersink the nail head as shown in Figure 8, and the only way that such countersinking can be kept uniform from one nail to the next is by driving the nail until the spindle positively engages the sleeve it in a lengthwise direction. It is desirable, therefore, to have a comparatively large spindle and sleeve area come into such engagement instantaneously to effect the limiting action. As shown in Figure 8, not only does the shoulder engage the bore entrance l8, but the entire length of taper l5 engages the flared portion I! of the sleeve to limit relative lengthwise movement of.

The stiffness of spring should not be excessive so as to require undue exertion by the operator to compress the spring in effecting relative advancement of the anvil bar through the sleeve for driving the nail. Moreover, an excessively stiff spring is to be avoided because such spring also constitutes a shock absorber which effectively isolates the sleeve ID from the rapid vibrations of the anvil bar to avoid impact of the workengaging end of the sleeve with the work unnecessarily during the driving operation until its very end, although such spring interconnects the two elements IE! and i2 and serves as the sole means for holding them together at all itmes.

When for any reason it is desired to disassemble the attachment, the sleeve It is quickly unthreaded from the outer end of spring 30 by a few turns of the sleeve and is slipped directly off the end of the anvil bar, followed by a similar unthreading and withdrawal of the spring itself from the anvil bar. Moreover, as no abutment shoulders or other interengaging elements are required for maintaining the sleeve normally on the cylindrical end portion 14 of the anvil bar, such cylindricalportion and the sleeve bore present, no.

complex machining or casting problems. Being unbroken by inwardly projecting abutment shoulder formations, notches or the 1ike,.the straight cylindrical portion ll of the sleeve will not sustain undue stress concentrations productive of premature crystallization of the metal. Moreover, its bearing area in the sleeve producing guiding support will be a maximum.

In the modification of Figure 4 the enlarged portion 22 of the anvil bar I2 is smooth and a single spring 34, comprising the two sections 26 and 30', replaces the two springs 26 and 30 of the form shown in Figure 1. The spring sections 26 and 30, although part of a single spring. correspond in general form, characteristics and function to the respective springs 26 and 30 in the previously described spring arrangement. If desired, these two spring sections may be formed of uniform diameter wire throughout the length of the composite spring and the relative stifiness of the two spring sections established independently by controlling the temper of each.

In the second spring modification, as shown in Figure 5, the last coil or turn at the inner. end'of the spring 30a, corresponding to spring 30 in the first-described form, is of increased diameter relative to the general body of the spring and is retained against the flange 24 of the anvil bar l2 by the constricting end of coupling spring 26 which overlaps such flange and such inner end of the spring 30a.

In Figure 6, the spring 30b, corresponding to spring 30 in Figure 1, is substantially longer than in the previous forms, having an enlarged inner end portion constituting a socket which threads over and upon the coupling spring 26 for the purpose of anchoring such inner end of spring 3% against relative displacement lengthwise of the anvil bar [2.

These and other possible convenient springconnecting arrangements for the nail-holding sleeve l0 and the anvil bar may be employed within the principle of the invention as set forth herein. Also, while these various spring arrangements have been described principally with reference to a spindle and sleeve structure such as shown in Figures 1 and 2, it will be evident that any of these constructions desired could be utilized in a nailer having the spindle and sleeve structure shown in Figures 7 and 8, because the struck end of the anvil bar and the supported end of the sleeve in this form of device are essentially the same as in the device of Figures 1 and 2.

I claim as my invention:

1. A nail-driving device comprising a recipro-.

cable anvil bar having an elongated nail-striking end portion, a nail-retaining sleeve having one end engageable with the work and adapted to receive a nai1 therein and having its other end slidably receiving said bars nail-striking end portion, normally extended and relaxed spring means extending lengthwise of said bar and having a first end portion reacting from means on said bar, and means connecting the second end' through said sleeve while said sleeve is bearing onthe work during driving of a nail.

2. The nail-driving device defined in claim 1, in which the spring means are of spiral shape encircling the anvil bar, and the means connecting the second end portion of the spring means to the sleeve include such end formed as a screw element, and a cooperating screw element on the sleeve engaged with said spring means screw element.

3. The nail-driving device defined in claim 2 in which the first end portion of the spiral spring means is formed as a screw socket, and the means on the bar from which such first end portion of the spring means reacts are thread means on the anvil bar engaged with such screw socket.

4. The nail-driving device defined in claim 1, in which the spring means are of spiral shape encircling the anvil bar and the first end portion of the spring means is formed as a screw socket, and the means on the bar from which such first end portion of the spring means reacts are thread means on the anvil bar engaged with such screw socket.

5. The nail-driving device defined in claim 1 for a percussion tool, in which the anvil bar has a flange remote from its nail-striking end portion, and spiral mounting spring means encircling the anvil bar, having a reduced portion overlapping and retentively engaging said flange and a body portion projecting from said reduced portion in a direction away from the sleeve and constituting a socket adapted to engage the end of the percussion tool for holding the nail-driving device thereon.

6.. The nail-driving device defined in claim 5, in which the normally extended and relaxed spring means encircles the anvil bar and the spiral mounting spring means constitutes the means on the bar from which the first end portion of the normally extended and relaxed spring means reacts, ccnvolutions thereof being wound upon convolutions of the mounting spring means.

7. A nail-driving device, comprising a nailholding sleeve having a bore including a portion of uniform cross section, a nail-driving rod having an end portion of uniform cross section received in and slidably engaged with said uniform cross-sectional sleeve bore portion for 1ongitudinal movement therein, a spiral spring including a portion encircling a portion of said rod exteriorly of said sleeve, spring-holding means securing one end of said spring to said rod at a location remote from said rods sleeve-engaged end, and means securing the other end or said spring to said sleeve, enabling said spring in relaxed condition to establish a predetermined longitudinal relationship between said sleeve and said rod with said rods sleeve-engaged end received in the sleeves bore and compressible by movement of said rod farther into said sleeve while exerting a resilient force tending to restore such predetermined longitudinal relationship between said rod and said sleeve.

8. A nail-driving device comprising a nail holding sleeve having a bore including a portion of uniform cross section and a flared opening through one end of such sleeve, a nail-driving rod having an end portion of uniform cross section entering said sleeve bore through said flared opening and slidably engaged with said uniform cross-sectional sleeve bore portion for longitudinal movement therein, and. having a portion tapered complementally to said flared sleeve opening and engageable therewith by relative longitudinal contracting movement of said sleeve and rod, a spiral spring including a portion encircling a portion of said rod exteriorly of said sleeve, spring holding means securing one end of said spring to said rod at a location remote from said rods sleeve-engaged end, and means securing the other end of said spring to said sleeve, enabling said spring in relaxed condition to establish a predetermined longitudinal relationship between said sleeve and said rod with said rods sleeve-engaged end received in the sleeve's bore and compressible by movement of said rod farther into said sleeve while exerting a resilient force tending to restore such predetermined longitudinal relationship between said rod and said sleeve.

9. A nail-driving device comprising a nailholding sleeve having one end thereof threaded externally and having a bore including a portion of uniform cross section, a nail-driving rod having an end portion of uniform cross section entering said sleeve bore through said externally threaded sleeve end and slidably engaged with said uniform cross-sectional sleeve bore portion for longitudinal movement therein, a spiral spring including a portion encircling a portion of said rod exteriorly of said sleeve and having one end threaded onto said exterior thread of said sleeve, and spring-holding means securing the other end of said spring to said rod at a location remote from said rods sleeve-engaged end, enabling said springs in relaxed condition to establish a predetermined longitudinal relationship between said sleeve and said rod with said rods sleeve-engaged end received in the sleeve's bore and compressible by movement of said rod farther into said sleeve while exerting a resilient force tending to restore such predetermined longitudinal relation between said sleeve and said rod.

10. A nail-driving device comprising a nailholding sleeve having a bore including a portion of uniform cross section, an enlarged entrance portion and a flared portion located between said uni-form cross section portion and said entrance portion, a nail-driving rod passing through said enlarged entrance portion and said flared portion of said sleeve bore and having an end portion of uniform cross section received in and slidably engaged with said uniform cross-sectional sleeve bore portion for longitudinal move ment therein, and having a shoulder complemental to said enlarged bore entrance portion and a portion tapered complementally to said flared sleeve bore portion, said rod shoulder being engageable with said bore entrance portion and said tapered rod portion being engageable with said flared sleeve bore portion simultaneously by relative longitudinal contracting movement of said sleeve and rod, and operable by engagement of such rod portions and their complemental sleeve bore portions to limit contracting movement of said sleeve and rod.

11. A nail-driving device comprising a naildriving rod, a nail-holding sleeve having a bore receiving an end of said rod and slidable upon said rod, a spiral spring encircling said rod,

means securing one end of said spring to said rod, and means securing the other end of said spring to said sleeve against movement of said sleeve relative to said other spring end in either direction directly lengthwise of said sleeve, said spring being of such length in its relaxed condition as to establish a spring-determined positional relationship between said sleeve and said rod when said sleeve is subjected lengthwise only to the influence of said spring, said nail-driving rod being at least as small as such sleeve bore and unencumbered for movement of said sleeve a substantial length of said rod when said sleeve and rod are in said spring-determined positional relationship.

12. The nail-driving device defined in claim 1 for a percussion tool, in which the spring means are of spiral shape encircling the anvil bar, the means on the bar from which the first end portion of the spring means reacts includes a flange on the anvil bar remote from its nail-striking end portion, engaged by the first end portion of the spring means, and the first end portion of the spring means continues from said flange in a direction away from the sleeve and is of progressively expanded size in such direction, constituting a socket adapted to engage the end of the percussion tool for holding the nail-driving device thereon.

13. The nail-driving device defined in claim 1 for a percussion tool, in which the spring means comprise a first spiral spring encircling the anvil bar, the means on the bar from which the first end portion of the spring means reacts includes a flange on the anvil bar remote from its nailstriking end portion, engaged by the first end portion of the spiral spring, a spiral mounting spring encircling the anvil bar and having a reduced end engaging and clamping to the anvil bar flange the first end portion of said first spiral spring and overlapping said anvil bar flange,

10 said spiral mounting spring having a body portion projecting from said reduced end in a direction away from the sleeve and constituting a socket adapted to engage the end of the percussion tool for holding the nail-driving device thereon.

MALCOLM H. FOX.

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